Measuring the instantaneous flow rate of liquids during rapid variations and during unit .DELTA.t of time is frequently required.
The known and customary flow meters can be divided into two groups: those counting units of flow (i.e. the flow) rate of the liquid and those measuring the flow speed.
The devices counting the flow rate may be e.g. piston meters, rotary wheel, or chamber-type wet or dry meters, etc.
The fuel gauges, the so-called consumption meters used in motor vehicles are actually also flow rate counters, because the quantity of the consumed fuels is measured during a certain time or distance interval. The averaging does not yield an adequate picture, because during the time of measuring--due to the road conditions, speed variations of the vehicle (acceleration, deceleration), in other words due to the load fluctuation of the motor--these instruments give results with highly varying error percentage for the measured interval of time or distance.
In the other group, i.e. the flow velocity meters the quantity can be measured based upon knowledge of the given cross section with the formula based on the flow speed: Q=Fc. However, the speed is influenced by several factors, such as pressure, specific gravity, heat, absolute temperature, contraction, viscosity. The speed variation--m/sec--mainly due to the differential pressure and specific weight variation of square root relationship--can be indicated with very complicated instruments and calculated with sliderules.
Speedometers functioning with throttling or ram pressure measurement are familiar, but these give the data only for the specific test, and neither these, nor the Prandtl-type tube--which functions by converting the speed to pressure--measure the flow rate, or display the result of the measurement.
The instrument according to the invention measures a varying flow rate of liquid and may be used for the setting and accurate measurement of the consumer demand of the various media in motion, water-, gasmeters, as well as for checking steam utilization of devices functioning with dry steam, for measuring the fuel consumption of internal combustion engines and vehicles, for measuring the liquids flowing in pipelines, and the friction resistance, pressure loss, etc. of pipelines. Through the shunt tripping, the instrument is applicable for measuring the varying quantity of liquid media flowing through in any quantity.
The instrument functions with throttling, in such a way that the differential pressure and variation of the liquid carried through the instrument for utilization is indicated in the quantity of the liquid. The adjustment of the instrument in connection with the specific weight variation of the liquid can be performed from the outside. The contraction, and discharge cross section in accordance with the liquid types are adjustable on the instrument similarly from the outside. The flow rate of liquid is indicated by the instrument on a logarithmic scale, which--when connected with further varying phenomenon--is suitable for the formation of new measuring units, such as Q/km, G/km, etc. The obtained values may instantaneously vary according to the time .DELTA..